Looking at times more like a winter storm than a summertime insect invasion, the thousands of creatures, also known locally as shadflies, reduced visibility for motorists before they died and fell to the ground in a ground covering of an inch.

Wrightsville Fire Chief Chad Livelsberger told Lancaster Online : "It was like a blizzard in June, but instead of snow, it was mayflies.

"It was very slick, almost like ice. When you go to pull out, all your tires would do was spin."

According to experts, the bugs, which hatch under the bridge, are attracted to the lights 10ft above the road.